I had the opposite problem once
At Reading Festival, really looking forward to Linkin Park (their first album is great, shut up), and bar the vocals they sound exactly the same as the CD, even down to the little record scratches and samples.

I doubt they were playing to a backing tape, I think they were just that well-rehearsed, but that utterly misses the point for me. You want songs extended, buggered about with a bit, or at least clearly live.
(Eukanuba, Fri 26 Jul 2013, 14:27, Reply)